With recent predictions about the exhaustion of existing energy resources such as petroleum and coal, interests in alternative energy capable of replacing these have been growing. As one of such alternative energy, fuel cells have received attention with advantages of being highly efficient, not emitting pollutants such as NOx and SOx, and having sufficient fuel to use.
Fuel cells are a power generating system converting chemical reaction energy of fuel and oxidizer to electric energy, and hydrogen, methanol and hydrocarbon such as butane are used as the fuel, and oxygen is typically used as the oxidizer.
Fuel cells include polymer electrolyte-type fuel cells (PEMFC), direct methanol-type fuel cells (DMFC), phosphoric acid-type fuel cells (PAFC), alkaline-type fuel cells (AFC), molten carbonate-type fuel cells (MCFC), solid oxide-type fuel cells (SOFC) and the like.
Among these, solid oxide-type fuel cells have high energy conversion efficiency, and interests on the solid oxide-type fuel cells are high.
The solid oxide-type fuel cell is formed with an electrolyte membrane, and a fuel electrode (anode) and an air electrode (cathode) formed on both surfaces of this electrolyte membrane. When referring to FIG. 1 showing a principle of electricity generation of a solid oxide-type fuel cell, air is electrochemically reduced in an air electrode to produce oxygen ions, and the produced oxygen ions are transferred to a fuel electrode through an electrolyte membrane. In the fuel electrode, fuel such as hydrogen, methanol and hydrocarbon such as butane is injected, and the fuel releases electrons while bonding to the oxygen ions and electrochemically oxidized to produce water. Through such a reaction, electrons migrate to an external circuit.